Lubricating compositions containing mixed salts



IUBRICATINGCOMPOSI'IIONS CONTAINING. M 6

MIXED SALTS Arnold J. Morway, Clark, NJ., assignor to Esso Research 2 s andEngineering Company, a corporation of Delaware No Drawing. Application September 17, 1957 Serial N0. 684,409

7 Claims. (Cl. 25232.7)

This invention relates to lubricating compositions con- .taining salts of dialkyl dithiophosphoric acid and to the process for making them. In particular, it relates to greases and lubricating fluids containing co-neutralized mixtures. of ,salts of acetic acid, intermediate molecular weight carboxylic acids and'a dialkyl dithiophosphoric acid and to their methods of preparation.

Mixed salts of low molecular weight carboxylic acids and intermediate or high molecular weight carboxylic acids or both which are useful in lubricating oils are known. These known mixtures have been used as grease thickeners and for imparting certain desirable, properties to fluid type lubricants. It has now been found that greases and lubricating fluids can be prepared from thickeners comprising mix tures of salts of a dialkyl dithiophosphoric acid, acetic acid, and intermediate molecular weight monocarboxylic acids. The salt mixtures are formed by co-neutralization of the corresponding acids with an alkaline earth metal base in situ in lubricating oil to form greases having higher load-carrying ability, reduced wear characteristics,

and a lower degree of thixotropy than greases thickened with the aforementioned known mixtures. Furthermore, the presence of the dithiophosphoric acid salt in theconeutralized mixtures acts as an oxidation inhibitor. Moreover, such low thixotropic greases are very plastic and are particularly useful in centralized lubrication systems because of their ease of pumping and their good slumping properties. Also, under high shearing stresses,

the greases of the invention do not solidify or channel wherein R is an aliphatic hydrocarbon radical having either a straight or branched chain and containing from 3 to 8 carbon atoms. .R' is the same or different from R and is also an aliphatic hydrocarbon radical having a carbon atoms. Examplesof specific compounds which can be used include:

Di-n-propyl' dithiophosphoric acid Di-n-butyl dithiophosphoric acid] Dihexyl dithiophosphoric acid Dioctyl dithiophosphoric acid Propyl hexyl dithiophosphoric acid The-intermediate molecular weightmonocarboxylic unsubstituted aliphatic monocarboxylic acids containing from. 8 to 12 carbon atoms per molecule. a mixture of caprylic, capric, and lauric acids which are obtained from coconut oil can be used. at

The metal component of the thickeners of this invention are chosen from the alkaline earth metals such as calcium, strontium, and barium. Calcium is particularly preferred due to its low cost and availability.- Mixtures of the above metals can be employed if desired. The metals are reacted with the acids in the form of metal bases such-as the alkaline earth metal hydroxides, oxides, and carbonates.

The mol ratio of the dialkyl dithiophosphoric acid to the intermediate molecular weight monocarboxylic' acids in the thickeners is in the range of 1:1 to 1:4. The mol ratio of the dialkyl dithiophosphoric acid and the intermediate molecular weight carboxylic acids combined to the acetic acid is in the range of from 1:25 to 1:15. In terms of parts by weight, excellent thickeners can be prepared from a mixture of 1 to 4 parts, preferably one part of dialkyl dithiophosphoric acid; 4 to 1 parts, preferably 2 to 1 parts of intermediate molecular weight monocarboxylic acids; and to 1 parts, preferably 5 to 1 parts of acetic acid; with suflicient alkaline earth metal base to neutralize the mixture of acids.

The lubricating compositions of the invention comprise from 50 to 98 wt. percent of a lubricating oil and from about 2 to 50 Wt. percent of the thickener. When a grease is desired, the composition will contain about 15 to 50 wt. percent, preferably to wt. percent of the thickener and about 50 to 85 wt. percent, preferably 60 I to 80 wt. percent lubricating oil; while for fluid lubricants the composition will contain from about 2 to 15 wt. percent, preferably 5 to 10 wt. percent of the thickener, and

about 85 to'98 wt. percent lubricating oil.

The choice of lubricating oil used as a menstruum for co-neutralization of the acids with an alkaline earth metal base depends on the particular use contemplated for the finished lubricant. A wide variety of mineral as well as synthetic lubricating oils can be used. In general, the

' lubricating oil has a viscosity within the range of about 60 to 2500 S.S.U. at 100? F. and about 35 to 200 S.S.U. at 210 F., a pour point of about +20 to -75 F. and a flash point of about 350 to 650 F. Oils having a viscosity index of 1007or higher are usually desirable, though oils having a low viscosity index can be employed. As previously mentioned, synthetic as well as mineral lubricat'ing oils can be employed as part or all of the liquid phase of the grease, and they include-synthetic lubricating'o'ils of the hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mercaptal, polyalkylene oxide, silicone, and similar types. Synthetic oils such as the ple diesters can also be used, e.g. di-2-ethylhexy1 sebacate',

straight branched chain andpcontaining f 3 3 ,di-isooctyl azelate and the complex esters For example,

sheet or. alcohols, or. both with dicarboxylic acids or monocarboxylic acids or both.

The dialkyl dithiophosphoric acids of the invention are prepared by reacting phosphorus pentasulfide with an ap- 4 of dihexyl dithiophosphoric ac'd was then added to the lime-oil dispersion slowly with agitation over 1 hour. No external heating was applied but the temperature rose to 160 F. during the addition.

propriate aliphatic alcohol or alcohols by techniques 5 allowed to cool and the agitation continued until the known to the art. temperature had subsided to about 100 to 120 F. The The reaction temperatures utilized for the co-neutralgrease was then passed through a Gaulin homogenizer ization of the acetic acid, intermediate molecular weight and inspected. monocarboxylic acids and the dialkyl dithiophosphoric EXAMPLE II acid in a lubricating oil menstruum are in the range of about l50 -'to 350FJ However, when temperatures in A grease was p ep e y first dlspsrsms 5 the lower end of this temperature range are utilized, the P Q6111; ydrated lime in 86.2 Percent Of K111161111 heat of reaction will generally increase, the temperature lubflcatlng l g a 3 0 of 1200 at of the reactionmixture." The temperature of reaction Then blend of -00 W Percent Of glaclal cet c is not critical, except that temperatures much above 350 mild, l f 0f Wecollnfi AAC acldst and F, hould not b e I d wt. percentof dlhexyl dithiophosphoric acid was added The reaction cantake'place by, intimately mixing th 0 mineral Oil at ifi p 0f 'I The metal base and lubricating oil and slowly'adding with resultmg product Was agitated, allqwsd to cool. nd-th n agitation a blend of the three. acids. The agitation can Passed through a Gaulin homogemlerbe continued and thetemperature allowed to dropto room temperature. However, the reaction temperature EXAMPLE HI P f ably is ai tained for about /2 h0 l1rS to A grease prepared in accordance with Example I was Sum compleflon or the salt formation. The mixtu heated to 320 F. in a steam kettle at 100 lbs. per square then be cooled, and a conventional additive added, 1 inch of steam pressure and the resultant semi.fluid ma. desired. The mixture can then be homogenized such. as f i l was G li homoggnized d bl d d wi h an by passing through a Gaulin homogenlzer orv a, Charlotte ual quantity of a lubricating oil having a viscosity 'of M 7 177.8 S.S.U. at 10.0 F. and a viscosity index of 110. lubllcatlllg QP U f tile. lHYeIltlon 2 The resulting blend was again Gaulin homogenized at prepared by co-neutrallzing the acids in all the lubricating I 5 000 lb per, square i h, oil which is required in the finished lubricating composition. Alternatively, the co-neutralization can take place EXAMPLE IV in less than all but in at least a dispersing portion of;the I V s lubricating-oil usedin the finished composition and then I q'p p mi i0 X P Q I as eated additional lubricating oil blended therewith to form the f to m a steam kettle at p squ' s q fi i h d rodugt steam pressure and then Gaulin homogenized. Theho The invention will be better understood by reference mogellized f was With an equal to the following examples which include the. preferred q y of a mmeral lubrlcatmg 011 havlng a vlscoslty 9 embodiments of the invention, 1200 S.S.U. at 100 F. The resulting blend Was again Gaulin homogenized at 5,000 lbs. per square inch. EXAMPLE I 40 The characteristics of the above lubricants and greases A grease was prepared by dispersing 7.8 wt. percent of are shown in the following Table I.

Table I Properties Example I Example II Example III Example IV- Appearance--. Smooth uniform. Smooth uniform Uniform fluid Uniform fluid grease. fluid. lubricant. lubricant. Dropping Point, F. 500+- Consistency:

Penetrations, 77 F., mm./10-

Unworked- ,310. Worked strokes. 320... Worked 100,000 Stroke 325.- Viscosity. S.S.U.:

100 19000-. 186.3 1395. 210 F 128.0--- 46.2 9018. Extreme pressure properties:

Almen test Gradual loading:

Wt. Carried 15; 1s 15- l5. 1 Pin Condition Excellent polished... Excellentpolished... Excellent polished... Excellent polished. Shock loading:

Wt. Carried 1H 15 15. 15. Pin Condition Excellent polished... Excellent polished... Excellent polished... Excellent polished. Timken Test: 50 lbs. load.. Pass; narrow scar-.. Pass; narrow scarv 4 Ball Wear Test: Scar Spot Diam., 0.23... 0.22-.- 0 0.22.

rzrgncflfioo r.p.m.l0 kg.1 hour i Centrifuge Test: hour, 1,500 r.p.m., i 1.5.... 0.75.. 0.5.

Percent Sediment.

hydrated lime in 77.8 wt. percent of a mineral lubricating As previously noted, the acids making up the salt mix- Oil having a viscosity of 45.3 S.S.U. at 210 F., a viscosity tures of the invention are co-neutralized in situ in mineral at F., and a viscosity index of 110. blend of 10.0 wt. percent of glacial acetic acid, 2.4wt. rcent' of Wecoline AAC acids, and 2.0 wt." percent weeglinetkirkc. acids has the following cornposltion; 20%

liiiirfc acid, 24% caprylic acid and 56% capric acid:

The mixture was thenv Table II LOAD-CARRYING TESTS N GREASES CONTAINING CALCIUM DIHEXYL DITHIOPHOSPHATE.

Grease similar in composition to Example II but formed Grease 0! Example I at 150 F. by separate addition of Calcium dihexyl ditbiophospbate Appearance Uniform fluid Product Calcium dihexyl dithiophospbate tends to settle out even after Gaulm homogenization. 4 Ball Wear Test: Scar Spot, Diam., mm 0.23-. 34. Almen Test:

Gradual Loading- Weights earried...-. 14 15. Pin Condition Excellent polished Slight scratching. Shock loading- Weights carried"... 1% 10. Pin Condition Excellent polished Sheared.

As seen form the above tables, excellent solid greases and fluid lubricants can be prepared wherein the thickener comprises a co-neutralized mixture of salts of acetic acid, intermediate molecular weight monocarboxylic acids and a dialkyl dithiophosphoric acid.

Various other additives can also be added to the lubricating compositions, such as detergents, oxidation inhibitors, viscosity index improvers, corrosion inhibitors, pour depressants, dyes, other grease thickeners, and the like, as known to those skilled in the art.

What is claimed is:

l. A lubricating composition comprising from 50 to 98 wt. percent of a lubricating oil having a viscosity in the range of 60 to 2500 S.S.U. at 100 F., and from 2 to 50 wt. percent of a thickener comprising a co-neutralized mixture of alkaline earth metal salts of acetic acid, intermediate molecular weight monocarboxylic acids having from 8 to 12 carbon atoms per molecule and a dialkyl dithiophosphoric acid having from 3 to 8 carbon atoms per alkyl group, the mole ratio of dithiophosphoric acid to intermediate molecular weight monocarboxylic acid being about 1:1 to 1:4, the mole ratio of dithiophosphoric acid and intermediate molecular weight monocarboxylic acids combined to acetic acid being in the range of from 1:2.5 to 1:15, said mixture being prepared ata temperature of about 150 to 350 F.

2. A lubricating grease composition according to claim 1 wherein the composition has from to 40 wt. percent thickener.

3. A fluid lubricating composition according to claim 1 wherein the composition has from 2 to 15 wt. percent thickener.

4. A lubricating composition comprising from 50 to 98 wt. percent of a lubricating oil having a viscosity in the range of 60 to 2500 S.S.U. at 100 F., and from 2 to 50 wt. percent of a thickener comprising a co-neutralized mixture of alkaline earth metal salts of 10 to 1 parts by weight of acetic acid, 4 to 1 parts by weight of intermediate molecular weight monocarboxylic acids having from 8 to 12 carbon atoms per molecule and 1 to 4 parts by weight of a dialkyl dithiophosphoric acid having from 3 to 8 carbon atoms per alkyl group, said mixture being prepared at a temperature of about 150 to 350 F.

5. A lubricating grease composition comprisinga major proportion of a mineral lubricating oil and from 20 to 40 wt. percent of a co-neutralized calcium salt mixture of from 10 to 1 parts by weight of acetic acid, 4 to 1 parts by weight of coconut oil acids and 1 to 4 parts by weight of dihexyl dithiophosphoric acid, said mixture being prepared at a temperature of about 150 to 350 F.

6. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and from S to 10 wt. percent of a coneutralized calcium salt mixture of from 10 to 1 parts by weight of acetic acid, 4 to 1 parts by weight of coconut oil acids and l to 4 parts by weight of dihexyl dithiophosphoric acid, said mixture being prepared at a temperature of about 150 to 350 F.

7. The process of preparing a lubricating composition comprising co-neutralizing with an alkaline earth metal base, and in a dispersingportion of a lubricating oil having a viscosity in the range of to 2500 S.S.U. at F., a mixture of acetic acid, intermediate molecular weight monocarboxylic acids having from 8 to 12 carbon atoms per molecule, and a dialkyl dithiophosphoric acid having from 3 to 8 carbon atoms per alkyl group at a temperature in the range of to 350 F., the mole ratio of dithiophosphoric acid and intermediate molecular weight monocarboxylic acids combined to acetic acid being in the rangeof from 1:2.5 to 1:15 and the mole ratio of dithiophosphoric acid to intermediate molecular weight monocarboxylic acid being about 1:1 to 1:4.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,985 Rutherford et a1 Aug. 19, 1941 2,343,213 Ashley Feb. 29, 1944 2,344,392 Cook et al. Mar. 14, 1944 2,364,283 Freuler Dec. 5, 1944 2,364,284 Freuler Dec. 5, 1944 

1. A LUBRICATING COMPOSITION COMPRISING FROM 50 TO 98 WT. PERCENT OF A LUBRICATING OIL HAVING A VISCOSITY IN THE RANGE OF 60 TO 2500 S.S.U. AT 100*F., AND FROM 2 TO 50 WT. PERCENT OF A THICKENER COMPRISING A CO-NEUTRALIZED MIXTURE OF ALKALINE EARTH METAL SALTS OF ACETIC ACID, INTERMEDIATE MOLECULAR WEIGHT MONOCARBOXYLIC ACIDS HAVING FROM 8 TO 12 CARBON ATOMS PER MOLECULE AND A DIALKYL DITHIOPHOSPHORIC ACID HAVING FROM 3 TO 8 CARBON ATOMS PER ALKYL GROUP, THE MOLE RATIO OF DITHIOPHOSPHORIC ACID TO INTERMEDIATE MOLECULAR WEIGHT MONOCARBOXYLIC ACID BEING ABOUT 1:1 TO 1:4, THE MOLE RATIO OF DITHIOPHOSPHORIC ACIDS AND INTERMEDIATE MOLECULAR WEIGHT MONOCARBOXYLIC ACIDS COMBINED TO ACETIC ACID BEING IN THE RANGE OF FROM 1:2.5 TO 1:15, SAID MIXTURE BEING PREPARED AT A TEMPERATURE OF ABOUT 150* TO 350*F. 